Apparatus for discharging granular material such as sand in foundries or the like



June 16, 1964 E. BUHRER EI'AL 3,137,412

APPARATUS FOR DISCHARGING GRANULAR MATERIAL SUCH AS SAND IN FOUNDRIES OR THE LIKE Filed May 10, 1961 4 Sheets-Sheet l INVENTOR$= Enwm B h y MAX was Li 29 bl Mum June 16, 1964 U R ETAL 3,137,412

APPARATUS FOR DISCHARGING GRANULAR MATERIAL SUCH AS SAND IN FOUNDRIES OR THE LIKE Filed May 10, 1961 4 Sheets-Sheet 2 [N VljNTORS ERWIN Bl JHRER, MAX WERN WWMMM A TTORNEY$ June 16, 1964 BUHRER ETAL 3,137,412

APPARATUS FOR DISCHARGING GRANULAR MATERIAL SUCH AS SAND IN FOUNDRIES OR THE LIKE 4 Sheets-Sheet 3 Filed May 10, 1961 [NVIzINTORS ERWIN BUHRER, BY MAX WERNLI WWW W A TTORNEYS Fig.3

Jude 16, 1964 E. BUHRER EIAL 3,137,412 APPARATUS FOR nxscmacmc GRANULAR'MATERIAL sucu AS 51mm IN FOUNDRIES OR THE LIKE 7 Filed May 10, 1961 4 Sheets-Sheet 4 as J 66 1 Fig- 4' INVENTORS: awn \R 8 United States Patent 3,137,412 APPARATUS FOR DISCHARGING GRANULAR MATERIAL SUCH AS SAND IN FOUNDRIES OR THE LIKE Erwin Biihrer, Breitenaustrasse 164, Schatlhausen, Switzerland, and Max Wernli, Schatfhausen, Switzerland; said Wernli assignor to said Biihrer Filed May 10, 1961, Ser. No. 109,205 Claims priority, application Switzerland May 13, 1960 13 Claims. (Cl. 22270) The present invention relates to a novel apparatus useable in foundries for discharging molding sand from a silo onto a strewing surface to a given height.

It is known to the art that the discharge of molding sand used in foundries from a silo has been developed to a state whereby a sieve is incorporated into the base closure of the silo and the molding sand is discharged through this sieved base by vibrations. It is also known that the discharge of molding sand from a silo can be carried out through a grid which is built into the base of the silo, which grid can impart vibrations during the sand discharging operation. Furthermore, a silo base is known which incorporates turning rods adapted to rotate in the silo base, such that the base can be alternatively opened and closed by the rotation of these rods.

All the foregoing inventions have the disadvantage that their construction is difficult or complicated. Moreover, their operation is dependent on the granulation size of the granular material to be discharged. Additionally, operation is dependent on whether this material is dry or moist and whether a clay bonding has been added and so forth. These variable factors in the physical properties of molding sands make the operation of such apparatus critical and restrict its discharging operations. Moreover, it is a specific feature of the previously mentioned equipment that only relatively small quantities of foundry sand can be discharged in a given unit of time. With such apparatus it is also not possible to loosely strew out foundry sand which has a tendency to thicken or compress.

Further, there is known a double-segmented closure which operates axially in a manner similar to a grab, the two segments of which meet approximately beneath the middle of the silo outlet. These segment members are arranged in such a manner that they can swivel outwardly and, thus, widen the outlet slot of the silo. Closing of the outlet takes place by virtue of the return movement of the segment members into their closed position. A variation of this system is also known whereby closing is effected by a single movable segment which, on swinging outwards, opens a slot on one side of the silo and, which, upon returning to the closed position closes the outlet of the silo. Furthermore, another system is known whereby a flat, sheet metal plate is arranged so as to be able to slide in the silo closure, thereby opening the silo outlet and reclosing this outlet upon returning to its closed position. The last mentioned apparatus has no application for the purposes of the invention in question because it does not permit of control of the height of the molding sand when discharged onto a given strewing surface.

The material discharge apparatus designed according to the teachings of the present invention is provided with a pair of independently movable shutter members defining swivelable segment members adapted to pivot on a common support. Each of these segment members is provided with a frame supporting an arcuate shaped closure plate for the discharge opening of a storage silo. A separate variable speed drive unit is provided for each seg ment member so that each segment member may be separately driven but in a controlled manner. The drive units for the respective segment members are operably interconnected via a control circuit such that the segment members may be started at different times wherein one segment member is caused to trail the other by a desired amount to provide an adjustable outlet slot through which sand or the like may be discharged. Additionally, the control circuit is designed such that the driving speed of the individual drive units for the respective segment members may be desirably controlled to accommodate for varying requirements of material discharge.

Accordingly, it is an important object of the present invention to provide means permitting control of the driva ing speed of separate drive motors for a pair of cooperable shutter means as well as the starting and lag of one shutter means with respect to another so that the size of a discharge slot may be positively controlled and varied in accordance with the requirements for discharge of a ma! terial.

It is an important object of the present invention to provide means for effectively controlling the dischargeof molding sand from a silo upon a strewing surface to a given height.

Another important object of the present invention is to provide means for controllably varying the outlet of a supply hopper for moldings and to thus regulate the discharge of said sand therefrom.

Still a further object of the present invention is to provide independently driven yet cooperable shutter members arranged and associated with one another so as to effectively control the discharge of molding sand from a supply hopper in a reliable and positive manner.

Another object of the present invention is to provide an apparatus for discharging molding sand from a supply silo in a positive and reliable manner wherein the effective size of the outlet of said supply silo for depositing sand upon a strewing surface is regulated by a pair of cooperable shutter members, each of which is powered by a separate drive member which are interconnected to one another.

These and still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and'modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

In the drawing: 7

FIGURE 1 is a side elevational view of an apparatus incorporating the features of the present invention;

FIGURE 2 is a cross-sectional view through this apparatus and taken along line IIII indicated in FIG- URE 1;

FIGURE 3 is a cross-sectional view taken through the machine embodying the present invention and taken along line III-III indicated in FIGURE 2; and

FIGURE 4 is a schematic illustration of the electrical control circuit for the apparatus shown in FIGURES 1-3. Referring now to the drawings, the apparatus shown in FIGURES 1-3 is provided with a molding box 21 of the type commonly employed in foundries, which is activated by a suitable molding machine and supported on a table 22. Molding sand is fed into a supply silo 23 from a suitable delivery apparatus such as the endless conveyor unit 51. s i 4 The supply silo 23 shown by way of example, is in the form of a truncated pyramid and is provided with wall portions which meet at right angles with one another so that sectional views taken in a horizontal plane disclosed a right-angled cross-section for said silo. At the upper end of the silo 23 there is provided an inlet opening 24 while the opposite end is provided with a lower r 3 discharge opening 25. The upper inlet opening 24 is provided with a smaller surface area than the lower discharge opening 25.

Shutter means in the form of a pair of cooperable segment members 26 and 27 are arranged in such a manner that they can move by rocking or swivelling independently from one another on the stub shafts 28 carried by the silo 23. The segment members 26, 27 include the frame portions 26b and 275, respectively, pivotably supported on the axially arranged shafts 28. Each frame portion 26b, 27!) carries an arcuate plate 26a and 27a, respectively, which may be designed as a portion of a cylindrical surface, which cylindrical surface portions 26a, 27a are of equal radius and constructed so that they can cooperatively rotate together. Either of the segment members 26, 27 and, more specifically, the respective arcuate plates 26a and 27a are so designed and arranged that each is capable of independently obturating the entire discharge opening 25 of the silo 23.

The silo 23 is fastened to and supported by the iron bars 56 arranged at the upper end of said silo. As best seen in FIGURE 1, the laterally arranged stub shafts 28 carry a support plate 29 which, in turn, supports a guide grating 74 cooperating with discharge opening 25. In FIGURE 3 there are shown partition walls 70, 71 and 72 which are arranged in the region of the discharge opening 25 of the silo 23. These partition walls 70, 71, 72 extend vertically and throughout the entire width of the silo 23. The lower edges of these partition walls are spaced equidistant from the lower discharge opening 25 of the silo 23. These partition walls are arranged at right angles to the direction of movement of the segment members 26 and 27 and are supported in the lower section of the silo proper. The partition walls 70, 71 and 72 are provided in order to prevent a cross concentration of granular material during the movement of the segments 26 and 27, whereby frictional forces between the granular material and the moving segments 26 and 27 is sectionally divided by the walls 70, 71 and 72 from the outer silo wall with the result that the pressure between the granular material and the segment members 26 and 27, respectively, is decreased.

The guide grating 74 is arranged below the path of movement of the segment members 26 and 27. This guide grating 74 is provided with a plurality of substantially vertically arranged plates or bars 73 with their side surfaces parallel to the partition walls 70, 71 and '72. The guide grating 74 prevents the movement of granular material in the direction of the moving segment members 26 and 27 during the discharging operation. The granular material falls freely and perpendicularly from the silo onto the strewing surface.

The segment members 26 and 27 are shown in the drawings in the form of a double wall frame provided with the rack or gear rim portions 31 and 32, respectively, and to which are attached the cams 33 and 34, respectively. The cam 33 of segment member 26 operates the limiting switches 35 and 36, whereas the same 34 of segment member 27 operates the limiting switches 37 and 38 for purposes of which will be described more fully hereinafter. The gear rim portion 31 is adapted to engage the teeth of a gear 39, which, in turn, is driven by an electric motor 40. Similarly, the gear rim portion 32 is adapted to engage the teeth of a gear 41 which, in turn, is driven by an electric motor 42. Segment member 27 is provided with the pivotal weights 43 and 47 which swivel on their respective axis 44, 48 (see FIGURE 2), which weights are placed in registry with the segment member 27 via the bolts 45 and 49 movable in the slotted links 46 and 50 provided at the upper end of said segment member 27. The pivotal weights 43 and 47 cooperate with buffer surfaces 53 and 54 provided on opposite sides of the silo 23. Thus, when the free falling weights 43 or 47 strike one or the other of the buffer surfaces 53 or 54 any sand adhering tothe inner walls of the silo is jarred loose to ensure that an even sand mass appears in the silo 23. In FIGURE 1 for convenience in illustration, weight 47 is shown in its two possible buffer surface contact positions. In FIGURES 1-3, as previously mentioned, an endless belt conveyor 51 is provided by means of which the foundry sand 52 may be introduced into the interior of the silo 23. Internally of the silo 23 is arranged feeler means 55 which cooperates with the delivery conveyor 51 to stop the latter when a predetermined amount of sand is deposited in said silo.

In FIGURE 4 there is schematically illustrated the basic electric circuit for the apparatus designed according to the teachings of the present invention and shown in FIGURES 1-3. The control of the entire apparatus is centered in and originates from a rotatable control drum 61 which is directly connected to a drive motor 62.

V This control drum 61 supplies current impulses to a contactor 63 (hereafter called a relay) and a change-over mechanism 64 (also hereafter called a relay). Numeral 65 represents a timing switch by means of which the motors 40 and 41 can be switched on in succession. The motor 40 operates the driving gear 39 provided for the segment member 26, and the motor 42 operates the driving gear 41 provided for the segment member 27. Also incorporated in the electric control circuit of the apparatus of the present invention is a driving motor 66 directly coupled with a generator 67. The motor 66 is of the pole changing type for 500, 1000 and 1500 revolutions per minute. For example, with 500 revolutions per minute of the motor 66, the generator 67 produces an alternating current having a frequency of 58 cycles per second. With 1000 revolutions per minute the generator 67 produces an alternating current having a frequency of 66 cycles per second, and at 1500 revolutions per minute the generator 67 produces an alternating current with a frequency of 75 cycles per second. The relay mechanisms 63 and 64 are so designed that the motors 40 and 41, for an equal period of time may be driven at different frequencies and, in this manner, caused to operate at different speeds in their operation of driving the segment members 26 and 27. The cam operated limit switches 35 and 36 for motor 40, and limit switches 37 and 38 for motor 41 serve to cut-off the power supply to the respective motors 40 or 41 when an associated limit switch 35, 36 or 37, 38 is actuated by cams 33 or 34, respectively. These limit switches may, for example, operate an auxiliary circuit which cooperates with relay 63 to cause the power supply to the respective drive motor 40, 41 to be interrupted.

The mode of operation of the apparatus shown in FIG- URES 1-4 of the drawings is as follows:

The endless belt conveyor 51 fills the silo 23 in a conventional manner with a sutiicient quantity of foundry sand until the feeler 55 is reached, and when such occurs, the endless belt conveyor 51 is caused to stop its feeding function as is known to the art. To obtain an even layer of foundry sand over the entire surface of the molding box 21 so that it becomes filled, it is necessary that the control drum 61 send an impulse to the relays 63 and 64. The change-over relay 64 actuates the drive motor 66 for the generator 67 so that a desired frequency is delivered to one of the reversible motors 40 or 41 via the relay 63. The relay 63 is so designed that it initially switches on the reversible drive motor 41 whereupon the segment portion 27 (FIGURE 1) swivels on the axle stub discharge opening 25 of the silo 23. The size of the discharge slot for the lower discharge opening 25 of the silo 23 is controlled by the setting of the timing switch 65. During this movement foundry sand drops from the silo 23 onto the molding box 21. When the cam 34 contacts the limit switch 37 the motor 41 becomes switched-off via relay 63. The segment member 27 then comes to a stop and meanwhile the segment member 26 causes the discharge slot which has been developing to close again, with the cam 33 also finally striking the limiting switch 36 whereupon the motor 40 also stops. During a subsequent work cycle, the segment members 26, 27 are driven by the reversible drive motors 40, 41 in an opposite rotational sense with the earns 33 and 34 finally contacting limit switches 35 and 38 to shut-off drive motors 40 and 41, respectively, in a manner as previously described.

The control drum 61 is directly coupled with the main drive motor 62. The impulses from the control drum 61 as already stated operate the relays 63 and 64. Thereby, the number of revolutions of the generator drive motor 66 is controlled so that the selection of the final number of poles is definite during the running time of the segment members 26 and 27. The generator 67 is driven by the drive motor 66 producing, according to the r.p.m. of the motor 66, an alternating current with a frequency of 58, 66 or 75 cycles per second. The current supplied to the motors 40 and 41 can be provided from four diferent available frequencies controlled by the relay 63 because, in addition, there is a direct connection in the electrical circuit with the alternating current supply having a frequency of 50 cycles per second. The relay 63 can, for example, be arranged to supply the motors 40 and 41 with currents of equal frequency so that the two segment members 26 and 27 are driven at approximately the same speed. In this instance, the discharge slot formed between the two segment members 26 and 27 varies as soon as the movement of the segments 26 and 27 takes place over the lower discharge opening 25 only by the amount of variation of the motors 40 and 41 from their rated speed. This variation is dependent upon the cumulative load. It therefore follows that the segments 26 and 27 operate at approximately equal speeds. As previously mentioned, during a subsequent work cycle, the direction of rotation of the segment members 26, 27 is reversed by the respective reversible motors 40, 41. Using the above mentioned apparatus it is possible to supply the drive motor 41 with a frequency of 50 cycles per second and the drive motor 40 with a frequency of 58, 66 or 75 cycles per second. This has the result that the segment 26 swivels faster than the segment 27 so that the discharge slot formed between the two segment members 26, 27 is reduced in size. The opposite result is also possible if the motor 41 is fed with a higher frequency than the motor 40, whereupon the discharge slot between the two segments 26 and 27 is continually extended. The sand discharging apparatus disclosed in FIGURES 1-3 can also be supplied with only a single frequency.

By virtue of the swivelling movement of the segment member 27, the falling weights 43 and 47 are lifted so that the slotted links 46 and 50 contact the bolts 45 and 49. As soon as the falling weights 43 and 47 move outwards a small degree over their dead-center position they fall to the opposite side and strike the buffer surfaces 53 and 54, respectively. The striking of these falling weights 43 and 47 on the buffer surfaces 53 and 54 fastened to the silo wall 23, causes any sand which adheres to the inside of the silo wall 23 to be loosened so that an equal sand mass is guaranteed internally of the silo 23. It is to be appreciated that each of the respective adjacently arranged end walls 260, 270 of frame portions 26b, 27b of segment members 26 and 27 are carried on a common pivot support shaft 28, which shafts 28 are arranged in axial alignment.

The hereinabove described apparatus renders possible the discharge of granular material of different granulation sizes, ditferent moisture content and possessing different bondings without encountering any difficulties. It is also possible to discharge granular materials with different flowabilities without experiencing difficulty. The previously described method of operation also makes possible without difliculty the discharge of granular material which by its nature tends to adhere to surfaces. By using the method described it is possible to discharge loosely and completely granular material in a loose form even though such material has a marked tendency to set or compress. This apparatus, compared with other known devices, has the further advantage that a greater discharge of material per given unit of time can be achieved. The described apparatus has proved particularly practical for strewing granular material such as molding sand on foundry batches of molds. When employed with automatic foundry molding machines this apparatus with very little control ensures the strewing of molding sand to an even height over foundry molds.

Having thus described the present invention what is desired to be secured by United States Letters Patent, is:

1. In an apparatus for discharging molding sand for foundries from a silo onto a strewing surface to a given height; a pair of cooperable yet separately driven movable segment members, means for pivotably supporting said pair of cooperable segment members, a separate drive unit operatively connected with each segment member for driving said segment members in trailing relation to one another to define an adjustable discharge slot, and control means cooperating with said drive units for operably interconnecting said drive units and for regulating the driving speed of each of said drive units with respect to one another in order to vary the size of said adjustable discharge slot.

2. A sand discharging apparatus comprising a supply silo having an inlet and outlet and adapted to store a quantity of molding sand, a pair of pivotal shutter means cooperating with said outlet to define an adjustable discharge slot for controlling the quantity of sand discharged through said outlet, a separate drive unit operatively connected with each of said shutter means to drive the latter in trailing relation with respect to one another during sand discharge, and control means operatively connected with said separate drive units for operably interconnecting said drive units to one another such that the size of said adjustable discharge slot may be varied and for varying the rotational speed of each drive unit to vary the size of said adjustable discharge slot and for successively energizing said drive units in timed relation to one another.

3. A sand discharging apparatus according to claim 2,

wherein each drive unit is a motor, the speed and direction of rotation of which can be regulated.

4. A sand discharging apparatus comprising a supply silo having an inlet and outlet and adapted to store a quantity of molding sand, a pair of pivotably mounted shutter means cooperating with said outlet to define an adjustable discharge slot for controlling the quantity of sand discharged through said outlet, each of said shutter means including a frame portion supporting an arcuate plate member capable of independently and completely obturating said outlet, said arcuate plate member of each shutter means being arranged in spaced relation to define said adjustable discharge slot, a separate drive unit operatively connected with each of said shutter means to drive said shutter means so as to follow one another during sand discharge, and control means operatively connected with said separate drive units for operably interconnecting said drive units to one another in order to control the speed of movement of said shutter means with respect to one another such that the size of said adjustable discharge slot may be varied.

5. A sand discharging apparatus comprising a supply silo having an inlet and outlet and adapted to store a quantity of molding sand, a pair of pivotably mounted shutter means cooperating with said outlet to define an adjustable discharge slot for controlling the quantity of sand discharged through said outlet, each of said shutter means including a frame portion supporting an arcuate plate member capable of independently and completely obturating said outlet, said arcuate plate member of each shutter means being arranged in spaced relation to define said adjustable discharge slot, a separate drive unit operatively connected with each of said shutter means to drive said shutter means in trailing relation with respect to one another, and control means including a control drum, relay means and a timing switch cooperating with said separate drive units for operably interconnecting said drive units to one another in order to control the speed of movement of said shutter means relative to one another such that the size of said adjustable discharge slot may be varied.

6. A sand discharging apparatus according to claim 5, said control means further including a generator, a drive motor for driving said generator at variable output frequencies to control the operational speed of said separate drive units.

7. A sand discharging apparatus comprising a supply silo having an inlet and outlet and adapted to store a quantity of molding sand, a pair of pivotably mounted shutter means cooperating with said outlet to define an adjustable discharge slot for controlling the quantity of sand discharged through said outlet, each of said shutter means including a frame portion supporting an arcuate plate member capable of independently and completely obturating said outlet, said arcuate plate member of each shutter means being arranged in spaced relation to define said adjustable discharge slot, a separate drive unit operatively connected With each of said shutter means to drive said shutter means so as to follow one another, and control means operatively connected with said separate drive units for operably interconnecting said drive units to one another to regulate'the speed of movement of said shutter means relative to one another such that the size of said adjustable discharge slot may be varied, said control means including limit switches for selectively rendering inoperative any of said separate drive units, and cam means in operable registry with said limit switches for actuating the latter.

8. A sand discharging apparatus according to claim [wherein said frame portion of each shutter means supports gear means driven by an associated drive unit.

. 9. Apparatus for discharging a flowable material, particularly for discharging molding sand for foundries from a supply hopper onto a strewing surface to a given height, which comprises: a supply hopper having an inlet and outlet and adapted to store a quantity of molding sand, a pair of independently movable segment members cooperating with said hopper outlet, common support means for movably supporting said pair of segment members, separate drive means operatively connected with each segment member for driving said segment members in spaced trailing relation to one another, to define an adjustable discharge slot in the region of said hopper outlet and between said spaced segment members, and control means cooperating with said separate drive means for operatively interconnecting said drive means. V

10. Apparatus for discharging a flowable material according to claim 9, wherein said control means includes means for changing the speed of said segment members during movement thereof to vary the size of said discharge slot.

11. Apparatus for discharging'a fiowable material according to claim 9, wherein said support means pivotably supports said pair of segment members about a common pivot axis.

12. Apparatus for discharging a fiowable material according to claim 9, including partition wall means arranged at the lower end of said supply hopper transverse to the direction of movement of said segment members, and dividing the interior of said supply hopper into spaced compartments. I v

13'. Apparatus for discharging a flowable material according to claim 9, including guide grating means arranged beneath said hopper outlet and extending across the entire outlet of said supply hopper.

References Cited in the file of this patent UNITED STATES PATENTS 2,437,302 Maxon Mar. 9, 1948 2,721,761 LeTourneau Oct. 25, 1955 2,739,797 Kemper Mar. 27, 1956 2,812,970 Martinson Nov. 12, 1957 OTHER REFERENCES German Printed Application, 1,025,108, Feb. 27, 1958. 

1. IN AN APPARATUS FOR DISCHARGING MOLDING SAND FOR FOUNDRIES FROM A SILO ONTO A STREWING SURFACE TO A GIVEN HEIGHT; A PAIR OF COOPERABLE YET SEPARATELY DRIVEN MOVABLE SEGMENT MEMBERS, MEANS FOR PIVOTABLY SUPPORTING SAID PAIR OF COOPERABLE SEGMENT MEMBERS, A SEPARATE DRIVE UNIT OPERATIVELY CONNECTED WITH EACH SEGMENT MEMBER FOR DRIVING SAID SEGMENT MEMBERS IN TRAILING RELATION TO ONE ANOTHER TO DEFINE AN ADJUSTABLE DISCHARGE SLOT, AND CONTROL MEANS COOPERATING WITH SAID DRIVE UNITS FOR OPERABLY INTERCONNECTING SAID DRIVE UNITS AND FOR REGULATING THE DRIVING SPEED OF EACH OF SAID DRIVE UNITS WITH RESPECT TO 